This invention relates generally to blow molding machines and particularly to a label transfer mechanism for transferring labels from a label storage magazine to an article forming mold cavity where the labels become molded into the formed article.
Blow molding machines are used to produce various articles including containers for household chemicals, beverages and other substances. In a typical blow molding process, a pair of mold halves are clamped together around a tube of molten thermoplastic material, known as a parison. The parison is then inflated by gas pressure so as to conform with the mold cavity. Frequently, labels are applied to the containers for product identification, instruction, warning, etc.
In the past, formed containers were sent to a separate work station where the labels were adhesively bonded to the container. More recently, however, a class of blow molding machines have been developed having in-mold labeling capabilities. In these machines, labels are transferred from a storage magazine and deposited directly into the mold cavity prior to forming of the article. Vacuum ports, within the mold halves, maintain the labels in position as the molds are clamped around the molten parison and the parison is inflated.
When the parison is inflated, the labels become thermally bonded to the container outer surface. This process of in-mold labeling provides a label which is durable and less likely to peel-off the container. More importantly, the finished container is aesthetically desirable since the label is molded flush with the container surface.
In accordance with this invention, a transfer assembly for an in-mold labeling machine is provided having a rotatable label carrier. The carrier indexes or stops periodically during rotation. The number of indexed positions associated with the carrier corresponds to the number of labeling stations employed in the particular production set-up.
As the carrier is indexed, labels, held in a label storage magazine, are transferred to positions on the label carrier where they are held by vacuum cups. The loaded carrier is next moved and indexed along a placement assembly where vacuum heads, mounted on the distal end of a placement arm, are pivoted between a retracted position and a position in registry with one of the labels so as to remove the label from the carrier. The carrier is then indexed and moved to the next station.
The moving and indexing of the carrier is successively repeated resulting in the labels being transferred from the carrier to each of the vacuum heads of the placement assembly. Once the carrier has moved past the placement assembly, the placement arm is raised upwardly and extended to place the labels onto the inner surface of the mold cavities where the labels are maintained by vacuum ports. The placement arm is retracted as the blow molding sequence begins.
During blow molding, platens cause the mold halves to be clamped together around a molten parison. The parison is inflated to conform to the mold cavity thereby forming the article and fusing the labels to the article outer surface.
Additional benefits and advantages of the present invention will become apparent to those skilled in the art to which this invention relates from the subsequent description of the preferred embodiments and the appended claims, taken in conjunction with the accompanying drawings.